UPSC Prelims 2018 · Question 99 of 99

UPSC Prelims 2018 question on Plant Disease Spread

Consider the following:

1. Birds
2. Dust blowing
3. Rain
4. Wind blowing

Which of the above spread plant diseases?

  1. 1 and 3 only
  2. 3 and 4 only
  3. 1, 2 and 4 only
  4. 1, 2, 3 and 4
Show answer

Answer: D. 1, 2, 3 and 4

Analysis

All four spread plant diseases, so the answer is (d) 1, 2, 3 and 4.

Agencies such as wind, water, animals, insects, mites, nematodes and birds are the recognised means of indirect transmission of the pathogens that cause plant disease. Birds, dust blowing, rain and wind blowing therefore all qualify, whether by carrying spores through the air, splashing them between plants, or moving infected material from one host to another.

Source

Resource on the transmission of plant diseases (reference material).

How to crack it

The reasoning chain runs from what a pathogen needs, namely a vehicle to move from one host to another, rather than from a memorised list of vectors. Any agent that physically carries particles between plants qualifies, and dust, rain, wind and birds all do. Item 2 looks like the intruder because dust is not alive, but transmission does not require a living carrier. When a list mixes living and non-living agents, ask whether the process demands life, and in mechanical transmission it does not.

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